Gulf of Maine Seasonal Sea Surface Temperature Update

Seasonal Patterns in Sea Surface Temperatures

Author

Adam Kemberling

Published

January 4, 2023

About the Updates:

Over the past decade, scientists at the Gulf of Maine Research Institute have led a body of research that highlights the rapid pace of warming in the Gulf of Maine. To keep you informed, we share seasonal updates about conditions in the Gulf of Maine.

Note About the Data: The figures in this report are created using remotely-sensed satellite data as part of publicly funded research efforts. Satellite SST data was obtained from NOAA’s National Center for Environmental Information (NCEI), with all maps and figures displaying NOAA’s Optimum Interpolation Sea Surface Temperature Data.

Note on Preliminary Data: This dataset has a 2-week latency period, during which values may change due to quality control measures. Any data within 14 days of the publishing date may be subject to change.

The Gulf of Maine Region

For analyses like these, it is important to be clear about the spatial extent that “defines” the Gulf of Maine (Figure 1), as different borders could produce different results. The spatial domain we use as the “Gulf of Maine” is displayed below. This area is consistent with previous reports and publications GMRI has produced.

Season Highlights

For this seasonal report we present an analysis of SST for fall (September 1st - November 30th) for the year 2022. This season the average SST for the Gulf of Maine was 60°F, making it the 2nd hottest fall on record for the period of 1982-2022 — the period over which the satellite data used are available. This seasonal average temperature is 4.44°F above the long-term (1982-2011) fall average of 55.56°F.

Weekly Temperatures

In the below table (Table 1), we highlight how the SST for each week this fall compares to a 30-year baseline period (i.e., climatological averages from 1982 through 2011).

The observed SST, long-term average SST, and SST anomalies (i.e., departures from the long-term average SST) are shown. As expected, SSTs in the fallbegin to drop as the season progresses, with anomalies showing no clear trend over the course of the season. Rather, departures from the long-term average hovered around 4°F above normal with a few weeks punctuated by anomalies in excess of 6°F.

Table 1: Observed, climatological average, and deviation from the climatological average (i.e., temperature anomaly) for SST at a weekly resolution in the Gulf of Maine during fall 2022.
One-Week Period	Observed Temperature		Climatological Average		Temperature Anomaly
Weekly Sea Surface Temperatures - Fall
(September 1st - November 30th)
One-Week Period	°F	°C	°F	°C	°F	°C
Sep 01 - Sep 03	66.60	19.20	61.50	16.40	5.14	2.85
Sep 04 - Sep 10	66.30	19.00	61.00	16.10	5.21	2.90
Sep 11 - Sep 17	65.40	18.60	60.30	15.70	5.07	2.82
Sep 18 - Sep 24	63.10	17.30	59.50	15.30	3.58	1.99
Sep 25 - Oct 01	60.70	15.90	58.60	14.80	2.13	1.18
Oct 02 - Oct 08	59.60	15.40	57.50	14.20	2.16	1.20
Oct 09 - Oct 15	59.40	15.20	56.30	13.50	3.05	1.69
Oct 16 - Oct 22	59.30	15.10	55.10	12.90	4.11	2.28
Oct 23 - Oct 29	59.50	15.30	54.00	12.20	5.56	3.09
Oct 30 - Nov 05	59.40	15.20	52.90	11.60	6.53	3.63
Nov 06 - Nov 12	58.40	14.70	51.90	11.00	6.57	3.65
Nov 13 - Nov 19	56.60	13.70	50.90	10.50	5.75	3.19
Nov 20 - Nov 26	53.80	12.10	49.90	9.94	3.93	2.18
Nov 27 - Nov 30	52.40	11.30	49.10	9.51	3.28	1.82
Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data.
Climatology Reference Period: 1982-2011.

Monthly Statistics

Looking at monthly averages (as opposed to week-by-week conditions Table 2), we see each month was 3.84°F or more above the 1982-2011 climatological average. November showed the largest deviation from the long-term climatological average, with an average SST anomaly of 5.33°F.

Table 2: Observed, climatological average, and deviation from the climatological average (i.e., temperature anomaly) for SST at a monthly resolution in the Gulf of Maine during spring 2022 (defined as March 1 through May 31).
Month	Observed Temperature		Climatological Average		Temperature Anomaly		Temperature Progression
Month	°F	°C	°F	°C	°F	°C	High/Low °F
Sep	64.30	17.90	60.10	15.60	4.17	2.32
Oct	59.50	15.30	55.70	13.10	3.84	2.13
Nov	56.30	13.50	50.90	10.50	5.33	2.96
Data Source: NOAA OISSTv2 Daily Sea Surface Temperature Data.
Climatology Reference Period: 1982-2011.

Seasonal Trends and Anomalies in Context

The Gulf of Maine is an area of particular interest to the scientific community because of the remarkable rate of warming it has experienced in recent years coupled with its importance as a major driver for the regional economy.

Figure 2: Average annual spring SSTs in the Gulf of Maine from 1982 through 2022. The solid red line indicates the trend for the full time series.

When looking at average fall temperatures from the beginning of the satellite record in 1982, there is a clear long-term increase, with SST’s warming at a rate of 1.16°F per decade. Recent warm fall SST anomalies are consistent with a thermal regime shift that occurred around 2010. This rate of warming is ~4x the rate that global ocean temperatures are warming during these same months, a rate of 0.26°F per decade.

Figure 3: Average annual fall SSTs in the Gulf of Maine from 1982 through 2022. The solid orange line indicates the trend for the full time series for the Gulf of Maine. A solid blue line indicates the trend for the full time series for the global oceans.

The unprecedented levels of warmth over the past decade or so are consistent with what researchers believe has been a distinct regime shift in terms of the major influences on SSTs in the Gulf of Maine. The drivers of this (e.g., a potential weakening of the Atlantic Meridional Overturning Circulation and widening of the Gulf Stream) have been well-documented in the peer-reviewed literature, including through research by GMRI scientists.

How Does 2022 Compare?

2022 is the 2nd warmest fall season observed in the Gulf of Maine during the 41 years we have satellite data to analyze. The top 5 warmest fall seasons have all occurred in the last decade.

Figure 4: An ranking of the 5 warmest fall seasons for the Gulf of Maine in the satellite record (1982-2022). 2022 is the 2nd warmest fall on record; the five warmest fall seasons have all occurred within the last decade.

Marine Heatwave Conditions

The most commonly used definition of a “marine heatwave” (MHW) is when daily average SST’s exceed the 90th percentile of a climatological (i.e., 30-year) average for at least 5 consecutive days. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event.

Using this broadly accepted definition, the Gulf of Maine has experienced MHW conditions for 96.7% of fall 2022. September 26th & October 3rd-5th were the only dates where SST was below the threshold for a MHW.

Figure 5: A timeseries of marine heatwave (MHW) conditions in the Gulf of Maine extending from January 1 through November 30, 2022. Black lines representing the long-term (i.e., 1982 – 2011) average SST, the 10th percentile, and 90th percentile for a given day in the Gulf of Maine are labelled to indicate climatological reference points; a solid line (red for marine heatwave or blue for a non-event) indicate the observed SST this year; red and blue shading illustrates how far the observed SST falls from the climatological mean.

Presenting SST conditions in terms of anomalies (Figure 6) as opposed to absolute values (Figure 5) illustrates in greater detail the magnitude of MHW conditions throughout the fall. The most extreme anomalies occurred in November, with temperatures exceeding \(6°\)F above the climatological average for a stretch of 16 days.

Figure 6: A timeseries of daily average SST anomalies in the Gulf of Maine (solid red line) compared to marine heatwave (MHW) conditions (dashed black line) in the Gulf of Maine for the period January 1 through November 30, 2022.

Heatmap of Temperature Anomalies and Heatwave Events

Looking at the full record of daily SST anomalies in the Gulf of Maine (Figure 7), the distinct thermal regime shift beginning around 2010 is evident. Indeed, since 2012, the Gulf of Maine has experienced far more persistent MHW conditions (indicated by solid black lines) than at any other point in the satellite record.

Figure 7: Heat map of daily SST anomalies from the beginning of 1982 through the fall of 2022. Not only do more large warm anomalies (darker reds) appear more frequently in recent years, but the frequency and duration of marine heatwave events (black lines) in the Gulf of Maine has become more pronounced in the past decade.

Monthly Rankings Heatmap

Figure 8: A heatmap displaying the average SST anomaly for each month, since the beginning of the satellite record in 1982. The number within each cell indicates the ranking of that month compared to the same month across all years (i.e., the ‘1’ in Nov 2022 indicates that month was the warmest November over the 41-year timeseries).

Spatial Distribution of Seasonal Anomalies

From a spatial perspective, the Gulf of Maine and surrounding areas experienced above average SST’s for much of the region during fall 2022, but the warmest patches were to the south and east of Georges Bank, mostly outside the domain analyzed in preceding sections. The highest seasonally averaged anomaly of any location above was 8.88°F.

Figure 9: Map of average SST anomalies for each grid cell in the satellite record for fall 2022. The box outlined by the black dashed line denotes the region of study for the analysis (see Figure 1). Darker red regions indicate warmer anomalies.

Monthly Temperature Anomalies

Average monthly SST anomalies are shown in Figure 10. The warmest anomalies were concentrated just south and east of the domain studied in this analysis in September and October, but by November, SST anomalies within the Gulf of Maine were equally hot. Monthly-averaged SST anomalies in the Gulf of Maine and the surrounding areas reached > 8°F warmer than during our climate reference period (1982-2011).

Figure 10: This series of maps shows the average monthly SST anomaly for September, October, and November 2022. The box outlined by the black dashed line denotes the region of study for the analysis. Darker red regions indicate warmer anomalies.

A Note on Data Sources:

NOAA_ERSST_V5 data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.ersst.v5.html.

NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.

Citing This Work

If you would like to cite this report, please use:

Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: 2021 the Hottest Year on Record. https://gmri.org/stories/warming-21

A work by Adam A. Kemberling

Akemberling@gmri.org